1. Field
This invention relates to the processing of produced gases from a producing well and more particularly to processing the produced gases to concentrate the hydrocarbon gas and to separate hydrocarbon gas, other useable gases or liquids, certain unusable gases including waste gases, and to place the waste gases in a suitable form for injection into an injection well separate from the producing well.
2. The Relevant Technology
Natural gas is widely used today for home heating and cooking. As used herein, the term “natural gas” means a variety of hydrocarbon gases that are produced from a well (i.e., a producing gas well) drilled or bored into the ground or earth. Produced gas is extracted from the producing well and may be processed at the wellhead to remove certain contaminants. Thereafter, it is sent by pipeline to a gas processing facility. The produced gas being delivered is a mixture of gases and, depending on the produced gas obtained, possibly some natural gas liquids (NGL) that are separated for use as a separate source of hydrocarbon products. The produced gas after removal of NGL may include in various proportions or quantities of one or more of methane (CH4) and other hydrocarbon gases such as ethane (C2H6) and propane (C3H8), as well as carbon dioxide (CO2), nitrogen (N2), helium (He), hydrogen sulfide (H2S), other gases, and water. The produced gas may also include smaller amounts of other materials such as particulates and liquids entrained in the gas. The mixtures vary typically based on the well, the geologic formation from which the well is producing, and the geographic area where the well is located (i.e., the “field”).
The gas processing facility receives a stream of produced gas from any one of several sources of produced gas including one or more pipelines which may be connected to receive gas from one or more producing wells owned or controlled by different parties or from one or more storage structures. The gas processing facility operates to separate useable gases from the unusable gases, and to remove natural gas liquids, if any. The usable gases include the desired hydrocarbon gases like methane, which are concentrated and separated from the unusable gases like carbon dioxide and hydrogen sulfide. The desired hydrocarbon gases are then separated from other gases and directed to a suitable pipeline for delivery to users. Also, some other gases in the produced gas may have commercial value such as, for example, helium, and those are separated and recovered for sale. The unusable gases are disposed in some cases by venting or flaring.
In some applications, carbon dioxide and nitrogen have been separated from the produced gas and sold for commercial use. Economic conditions and other factors, however, are such that carbon dioxide and nitrogen are being vented to the atmosphere and not recovered.
A variety of processes have been developed for processing streams of gases including produced gas. For example, processes are available for drying gas, for removing contaminants, for separating the different gases in a stream, for concentrating certain gases and for gas effluent cleanup. A number of available processes are summarized in HYDROCARBON PROCESSING, May 2002 (Gulf Publishing Co.), (Gas Processes 2002 at pages 63-122). Suitable processes for treating streams of produced gases are described at pages 80 and 81.
Venting hydrogen sulfide gas into the atmosphere is not desired because it has an unpleasant scent or odor. Venting carbon dioxide may be deemed to be ecologically unsuitable or undesirable particularly in the quantities that may be involved in the processing of produced gas from a producing well.
Disposing of the carbon dioxide gas into an injection well is a recognized practice. Using the carbon dioxide gas to stimulate production from producing wells is also known. But processes to rapidly remove and dispose of unusable gases like carbon dioxide and hydrogen sulfide are not known. Rapid and ecologically acceptable disposal of waste gases including carbon dioxide separated from a produced gas in a manner to enhance producing well production are also not known particularly.